Simulators for assisting the teaching of observational astronomy. Part II: Photometry of normal and variable stars in total visible light

Abstract

For pt.I see ibid., vol.4, p.77-81 (1983). A simulator is described which, viewed with a commercial photomultiplier photometer, enables students to practise some of the techniques of quantitative stellar photometry in the laboratory. A fictitious open cluster is presented which contains stars of differing colours and apparent magnitudes. When a switch is closed, four of these stars undergo regular cyclic variations in brightness, with patterns typical of Algol, beta Lyrae, and Cepheid-type variables. From their own and given data, students can subsequently calculate apparent and absolute magnitudes, light curves, distances, etc., obtaining results comparable with corresponding objects in the real sky.

Simulators for assisting the teaching of observational astronomy. Part III: UBV photometry

“…By the defined conventions they then know that, for this star, m , = m , = mv= 6.50, and (U-B) and (B -V) = 0. Combining this information with their own measured values of l,, l , and 1, it is then possible to calculate the apparent magnitudes m,, m, and mv of all the other stars by Pogson's equation (Mills 1983). (U-B) and (B-V) may then be determined, as well as the colour temperature T , of each star.…”

“…(A graphical presentation constructed from data given by Allen (1976) is supplied to the students.) Knowing both Mv and mv, the distance of the star may readily be calculated (Mills 1983). The results are included in table 2 .…”

“…This paper continues the theme of parts I and I1 (Mills et al 1983, Mills 1983, namely to describe the construction of realistic simulators with which undergraduates may be introduced to modern techniques of observational astronomy during normal laboratory hours.…”

“…Johnson and Morgan adhered to this convention when establishing the characteristics of standard stars in their system, the 'corrected' apparent magnitudes being symbolised by the capital letters U, B and V. However, rather than quoting these figures directly, it has become customary in modern literature to show only V and the differences between the magnitudes found in other regions of the spectrum, symbolising these as (U-B) and (B -V). By definition (Mills 1983) the latter correspond to the ratios of brightness / , / I B and lB/lv.…”